We are looking for accomodation for 2 adults, 2 children for Dec. 25, 26, 27, 28 north of La Jolla near la Costa preferabley on or near the ocean-moderatley priced. Any suggestions?

Given your geographical paramenters, I suggest you consider a hotel in Del Mar, Encinitas, or Carlsbad. Some possibilities are:

Best Western Stratford Inn (stratfordinndelmar.com),

Hilton Garden Inn (hiltoncarlsbad.com),

Cardiff by the Sea Lodge (cardifflodge.com)

Encinitas Inn and Suites at Moonlight Beach (http://www.beachcalifornia.com/encbestw.html)

Holiday Inn Carlsbad-by-the Sea (carlsbadhi.com)

Grand Pacific Palisades Resort and Hotel (grandpacificpalisades.com)

You could also try the Oceanside Marina Inn, which is on Oceanside Harbor (omihotelcom)

Tripadvisor.com is a good resource for hotel reviews. I hope you enjoy your stay in the San Diego area.

There is also a Hilton in Del Mar (Del Mar Hilton North San Diego), which unless it has undergone renovation might be a little dated.
Plus a Courtyard by Marriott in Solana Beach.
Descriptions of both on the respective chain websites.

Best Western Stratford in Del Mar would be a good spot for families. Nothing fancy, but just a short walk (100 feet?) from the ocean.

The Grand Pacific Palisades in Carlsbad was nice when we stayed there a few years ago.
It is next door to Legoland, a few miles from the ocean (some rooms have a distant ocean view, about a mile from an outlet mall, and only a few miles from La Costa.
It will probably be too cold to do any swimming or sunbathing at that time of year.